Abstract: Based on the meteorological data of Zhangjiang, reference crop evapotranspiration were calculated by six different methods. Penman-Monteith method is taken as the standard; applicability of other methods is evaluated. The results show that annual mean reference crop evapotranspiration of Hargreaves-Samani and FAO56 Penman-Monteith is no significant difference. Mean monthly reference crop evapotranspiration of five methods and FAO56 Penman-Monteith have significant difference except specific month. The mean square deviations of ET0 between five methods and P-M method show difference with time scales. The mean square deviations of daily ET0 between 1948 Penman and P-M method is least, the following is Irmark-Allen. The mean square deviations of ten days ET0 between 1948 Penman and P-M method is least, the following are Irmark-Allen and Hargreaves-Samani. The mean square deviations of monthly ET0 between Hargreaves-Samani and P-M method is least, the following is 1948 Penman. Correlation coefficient of 1948 Penman, FAO24 Penman and FAO56 Penman-Monteith are the most volumes, that of Priestley-Taylor, Irmark-Allen are in middle, that of Hargreaves-Samani is the smallest volume.